Cyanogen chloride is a valuable intermediate product, chiefly for the production of guanidines and cyanuric chloride. In these and other processes the purity of the cyanogen chloride is of decisive significance.
Thus, e.g. a content of free chlorine in the cyanogen chloride acts disturbingly in the production of guanidines, while in the catalytic trimerization of cyanogen chloride to cyanuric chloride above all water, hydrogen cyanide and organic vapors are disturbing because they act as catalyst poisons; on the other hand a certain content of free chlorine is favorable.
Industrial cyanogen chloride can contain among others hydrogen cyanide, hydrogen chloride, chlorine, water, carbon dioxide, nitrogen and organic hydrocarbons either individually or in admixture with each other.
In the methods used in the art for the production of cyanogen chloride by reaction of hydrogen cyanide and chlorine in aqueous medium, see e.g. German Pat. No. 827,358, Heuser U.S. Pat. No. 1,588,731 and Trickey U.S. Pat. No. 3,197,273, it is generally easy to carry out the process in such fashion that the cyanogen chloride, in case it is desired, is obtained practically without substantial free chlorine impurities on the other hand, e.g., according to German OS No. 2521580 there can be obtained cyanogen chloride containing chlorine.
The water content in the cyanogen chloride is the cause of catalyst poisoning in the trimerization and of other unpleasant reactions since water causes the saponification of cyanogen chloride to ammonium chloride in which case the hydrolysis is still further accelerated by the presence of hydrogen chloride. As is known, ammonium chloride can lead to powerful explosions through the formation of nitrogen trichloride.
Therefore there have been proposed a number of purification or drying processes for removal of water from industrial cyanogen chloride. They all require for removal of the water content additional expense in the form of drying towers with drying agents or molecular sieves, which must regularly be loaded or regenerated, in the case where this is in general possible, which require expense for energy and operating and let waste air or waste water be formed. The water content in cyanogen chloride attainable with drying agents is between 0.05 and 0.2 weight %.
The purpose of the invention is to develop a distillation process for the purification of crude water, containing cyanogen chloride.